A capacitor or a reactor, which serves as a phase modifier, is connected to a system through a circuit breaker and used to modify the phase of a system voltage.
In general, there is a possibility in that when the phase modifier is closed in the system through the circuit breaker, a surge voltage or an inrush current may be generated in the phase modifier depending on the timing at which the circuit breaker is closed.
A so-called “circuit breaker” with an input resistance is a commonly-known method of suppressing the surge voltage or the inrush current described above.
For example, a circuit breaker with an input resistance described in FIG. 10 in Patent Literature 1 includes a resistor connected in parallel to the circuit breaker, and a switch connected in series to this resistor and connected in parallel to the circuit breaker.
In the conventional circuit breaker with an input resistance as described above, when a capacitor that serves as a phase modifier is to be closed, first a switch is closed to apply a power-supply voltage to the capacitor. A current generated by a transient surge voltage at the time when the resistance is input is sharply attenuated by the resistor. Therefore, the capacitor is applied with a voltage with the same frequency as that of the power-supply voltage and an amplitude lower than that of the power-supply voltage. Thereafter, when a main contact of the circuit breaker is closed, an inrush current that flows to the capacitor is suppressed because the capacitor has been already applied with the voltage an amplitude of which is lower than that of the power-supply voltage, through the resistor.